Replace (repair) the exhaust sensor this looks like a transistor with the middle leg cut off. it is situated below the lint filter but can only accessed by removing the back panel, top panel (or rear screws to allow the removal of the drum). drum and then front panel to remove the connector from the mainboard. If you follow the exhaust tube once the back is off you will see a single phillips head screw that is the sensor. check the wires to the circuit board are not broken or dry joints or just replace it. sorry i had a spare machine i scavenged from to fix my problem so i dont know where to buy new.